/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_lattice_q31.c
*
* Description:	Q31 FIR lattice filter processing function.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup FIR_Lattice
 * @{
 */


/**
 * @brief Processing function for the Q31 FIR lattice filter.
 * @param[in]  *S        points to an instance of the Q31 FIR lattice structure.
 * @param[in]  *pSrc     points to the block of input data.
 * @param[out] *pDst     points to the block of output data
 * @param[in]  blockSize number of samples to process.
 * @return none.
 *
 * @details
 * <b>Scaling and Overflow Behavior:</b>
 * In order to avoid overflows the input signal must be scaled down by 2*log2(numStages) bits.
 */

#ifndef ARM_MATH_CM0

/* Run the below code for Cortex-M4 and Cortex-M3 */

void arm_fir_lattice_q31(
    const arm_fir_lattice_instance_q31* S,
    q31_t* pSrc,
    q31_t* pDst,
    uint32_t blockSize)
{
	q31_t* pState;                                 /* State pointer */
	q31_t* pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
	q31_t* px;                                     /* temporary state pointer */
	q31_t* pk;                                     /* temporary coefficient pointer */
	q31_t fcurr1, fnext1, gcurr1 = 0, gnext1;      /* temporary variables for first sample in loop unrolling */
	q31_t fcurr2, fnext2, gnext2;                  /* temporary variables for second sample in loop unrolling */
	uint32_t numStages = S->numStages;             /* Length of the filter */
	uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */
	q31_t k;

	pState = &S->pState[0];

	blkCnt = blockSize >> 1u;

	/* First part of the processing with loop unrolling.  Compute 2 outputs at a time.
	   a second loop below computes the remaining 1 sample. */
	while(blkCnt > 0u) {
		/* f0(n) = x(n) */
		fcurr1 = *pSrc++;

		/* f0(n) = x(n) */
		fcurr2 = *pSrc++;

		/* Initialize coeff pointer */
		pk = (pCoeffs);

		/* Initialize state pointer */
		px = pState;

		/* read g0(n - 1) from state buffer */
		gcurr1 = *px;

		/* Read the reflection coefficient */
		k = *pk++;

		/* for sample 1 processing */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext1 = (q31_t)(((q63_t) gcurr1 * k) >> 32);

		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext1 = (q31_t)(((q63_t) fcurr1 * (k)) >> 32);
		fnext1 = fcurr1 + (fnext1 << 1u);
		gnext1 = gcurr1 + (gnext1 << 1u);

		/* for sample 1 processing */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext2 = (q31_t)(((q63_t) fcurr1 * k) >> 32);

		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext2 = (q31_t)(((q63_t) fcurr2 * (k)) >> 32);
		fnext2 = fcurr2 + (fnext2 << 1u);
		gnext2 = fcurr1 + (gnext2 << 1u);

		/* save g1(n) in state buffer */
		*px++ = fcurr2;

		/* f1(n) is saved in fcurr1
		   for next stage processing */
		fcurr1 = fnext1;
		fcurr2 = fnext2;

		stageCnt = (numStages - 1u);

		/* stage loop */
		while(stageCnt > 0u) {

			/* Read the reflection coefficient */
			k = *pk++;

			/* read g2(n) from state buffer */
			gcurr1 = *px;

			/* save g1(n) in state buffer */
			*px++ = gnext2;

			/* Sample processing for K2, K3.... */
			/* f2(n) = f1(n) +  K2 * g1(n-1) */
			fnext1 = (q31_t)(((q63_t) gcurr1 * k) >> 32);
			fnext2 = (q31_t)(((q63_t) gnext1 * k) >> 32);

			fnext1 = fcurr1 + (fnext1 << 1u);
			fnext2 = fcurr2 + (fnext2 << 1u);

			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			gnext2 = (q31_t)(((q63_t) fcurr2 * (k)) >> 32);
			gnext2 = gnext1 + (gnext2 << 1u);

			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			gnext1 = (q31_t)(((q63_t) fcurr1 * (k)) >> 32);
			gnext1 = gcurr1 + (gnext1 << 1u);

			/* f1(n) is saved in fcurr1
			   for next stage processing */
			fcurr1 = fnext1;
			fcurr2 = fnext2;

			stageCnt--;

		}

		/* y(n) = fN(n) */
		*pDst++ = fcurr1;
		*pDst++ = fcurr2;

		blkCnt--;

	}

	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
	 ** No loop unrolling is used. */
	blkCnt = blockSize % 0x2u;

	while(blkCnt > 0u) {
		/* f0(n) = x(n) */
		fcurr1 = *pSrc++;

		/* Initialize coeff pointer */
		pk = (pCoeffs);

		/* Initialize state pointer */
		px = pState;

		/* read g0(n - 1) from state buffer */
		gcurr1 = *px;

		/* Read the reflection coefficient */
		k = *pk++;

		/* for sample 1 processing */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext1 = (q31_t)(((q63_t) gcurr1 * k) >> 32);
		fnext1 = fcurr1 + (fnext1 << 1u);

		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext1 = (q31_t)(((q63_t) fcurr1 * (k)) >> 32);
		gnext1 = gcurr1 + (gnext1 << 1u);

		/* save g1(n) in state buffer */
		*px++ = fcurr1;

		/* f1(n) is saved in fcurr1
		   for next stage processing */
		fcurr1 = fnext1;

		stageCnt = (numStages - 1u);

		/* stage loop */
		while(stageCnt > 0u) {
			/* Read the reflection coefficient */
			k = *pk++;

			/* read g2(n) from state buffer */
			gcurr1 = *px;

			/* save g1(n) in state buffer */
			*px++ = gnext1;

			/* Sample processing for K2, K3.... */
			/* f2(n) = f1(n) +  K2 * g1(n-1) */
			fnext1 = (q31_t)(((q63_t) gcurr1 * k) >> 32);
			fnext1 = fcurr1 + (fnext1 << 1u);

			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			gnext1 = (q31_t)(((q63_t) fcurr1 * (k)) >> 32);
			gnext1 = gcurr1 + (gnext1 << 1u);

			/* f1(n) is saved in fcurr1
			   for next stage processing */
			fcurr1 = fnext1;

			stageCnt--;

		}


		/* y(n) = fN(n) */
		*pDst++ = fcurr1;

		blkCnt--;

	}


}


#else

/* Run the below code for Cortex-M0 */

void arm_fir_lattice_q31(
    const arm_fir_lattice_instance_q31* S,
    q31_t* pSrc,
    q31_t* pDst,
    uint32_t blockSize)
{
	q31_t* pState;                                 /* State pointer */
	q31_t* pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
	q31_t* px;                                     /* temporary state pointer */
	q31_t* pk;                                     /* temporary coefficient pointer */
	q31_t fcurr, fnext, gcurr, gnext;              /* temporary variables */
	uint32_t numStages = S->numStages;             /* Length of the filter */
	uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */

	pState = &S->pState[0];

	blkCnt = blockSize;

	while(blkCnt > 0u) {
		/* f0(n) = x(n) */
		fcurr = *pSrc++;

		/* Initialize coeff pointer */
		pk = (pCoeffs);

		/* Initialize state pointer */
		px = pState;

		/* read g0(n-1) from state buffer */
		gcurr = *px;

		/* for sample 1 processing */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext = (q31_t)(((q63_t) gcurr * (*pk)) >> 31) + fcurr;
		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext = (q31_t)(((q63_t) fcurr * (*pk++)) >> 31) + gcurr;
		/* save g1(n) in state buffer */
		*px++ = fcurr;

		/* f1(n) is saved in fcurr1
		   for next stage processing */
		fcurr = fnext;

		stageCnt = (numStages - 1u);

		/* stage loop */
		while(stageCnt > 0u) {
			/* read g2(n) from state buffer */
			gcurr = *px;

			/* save g1(n) in state buffer */
			*px++ = gnext;

			/* Sample processing for K2, K3.... */
			/* f2(n) = f1(n) +  K2 * g1(n-1) */
			fnext = (q31_t)(((q63_t) gcurr * (*pk)) >> 31) + fcurr;
			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			gnext = (q31_t)(((q63_t) fcurr * (*pk++)) >> 31) + gcurr;

			/* f1(n) is saved in fcurr1
			   for next stage processing */
			fcurr = fnext;

			stageCnt--;

		}

		/* y(n) = fN(n) */
		*pDst++ = fcurr;

		blkCnt--;

	}

}

#endif /*   #ifndef ARM_MATH_CM0 */


/**
 * @} end of FIR_Lattice group
 */
